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Railroad Valley

The dry lakebed of Railroad Valley Playa, Nevada is located at 1350 m above sea level (38.504° N latitude, 115.692° W longitude). It is a desert site with no vegetation with an overall size approximately 15 km by 15 km.

Typical atmospheric conditions at the site include an average aerosol optical depth at 550 nm of 0.060 [1]. The reflectance of the playa is generally greater than 0.3 and relatively flat spectrally except for the blue portion of the spectrum and an absorption feature in the shortwave infrared. Ground-based measurements of the directional reflectance characteristics of the playa show it to be nearly lambertian out to view angles of 30 degrees for incident solar zenith angles seen for overpasses of Terra and Landsat. [2]

Temporal records for this site show reflectance variations as a function of time of year, with lowest reflectance in the winter months due to a rising water table. The accuracy of vicarious calibration experiments over land is highly dependent on the choice of an appropriate calibration target. Ideally, such a calibration site should be flat, bright, spatially uniform, spectrally stable over time, near lambertian for small angles off nadir, and of sufficiently large spatial extent. Desert playas are preferred for vicarious calibration of moderate spatial resolution sensors due to their optical properties, predictably sunny conditions and low atmospheric aerosol loading.